Francisc Potmischil

The paper presents the experimental and DFT‐calculated values of the ¹³C NMR chemical shifts of the six stereoisomers of tetradecahydroacridine and of the corresponding nitrosamines. Performing the DFT calculations using several combinations of functional and basis sets, it was found that the best experimental‐calculated agreement was obtained for OPBE/6–311++G (dp) method. Considering the effect of N‐nitrosation upon the ¹³C NMR chemical shifts of the C‐α carbons of secondary amines, it was found that if following nitrosation both C‐α carbons are shifted upfield or both are shifted downfield, then the resulted nitrosamine will have a sterically strained ─N═O group. If, however, one of the C‐α is shifted upfield and the other is shifted downfield, then the ─N═O group will be strain‐free or weakly strained. Our calculations predict strain energies of about 10–15 kcal mol⁻¹ in the first case and ≈0–6 kcal mol⁻¹ in the latter.

Two kinds of good linear correlations were found between the chemical shifts of saturated six‐membered azaheterocyclic N‐methylamine N‐oxides and the chemical shifts of the methiodides of their parent amines. One of the correlations occurs between the ¹⁷O chemical shift of the N⁺―O^– oxygen in the N‐oxides and the ¹³C chemical shift of the N⁺―CH₃ methyl group analogously situated in the appropriate methiodide (r = 0.9778). This correlation enables unambiguous configuration assignment of the N⁺―O^– bond, even if the experimentally observed ¹⁷O chemical shift of only one N‐epimer is available, provided the ¹³C chemical shifts of both N⁺―CH₃ groups in the methiodide are known and assigned; furthermore, it can be used also for the estimation of ¹⁷O chemical shifts of the N⁺―O^– oxygens in N‐epimeric pairs of N‐oxides, for which observed ¹⁷O data hardly become available. The second correlation is observed between the ¹³C chemical shift of the N⁺―CH₃ methyl group in the N‐oxides and the ¹³C chemical shift of the N⁺―CH₃ methyl group analogously situated in the appropriate methiodide (r = 0.9785). It can be used for safe configuration assignment of the N⁺―CH₃ group and, indirectly, also of the N⁺―O^– bond in an amine N‐oxide, even if no ¹⁷O NMR data, and the ¹³C chemical shift of only one N‐epimer is available. Copyright © 2015 John Wiley & Sons, Ltd.

The ¹H and ¹³C NMR chemical shifts of 1,2,3,4,5,6,7,8‐octahydroacridine, 12 of its 9‐substituted derivatives, and of the corresponding N‐oxides were determined, assigned, and discussed in terms of 9‐substituent effects and effects of N‐oxidation. A good linear correlation was found between the ¹³C chemical shifts of the aromatic carbons in octahydroacridines and those of respective carbons in the corresponding N‐oxides. Copyright © 2009 John Wiley & Sons, Ltd.

The ¹⁵N chemical shifts of 13 N‐methylpiperidine‐derived mono‐, bi‐ and tricycloaliphatic tertiary amines, their methiodides and their N‐epimeric pairs of N‐oxides were measured, and the contributions of specific structural parameters to the chemical shifts were determined by multilinear regression analysis. Within the examined compounds, the effects of N‐oxidation upon the ¹⁵N chemical shifts of the amines vary from +56 ppm to +90 ppm (deshielding), of which approx. +67.7 ppm is due to the inductive effect of the incoming N⁺O⁻ oxygen atom, whereas the rest is due to the additive shift effects of the various C‐alkyl substituents of the piperidine ring. The effects of quaternization vary from −3.1 ppm to +29.3 ppm, of which approx. +8.9 ppm is due to the inductive effect of the incoming N⁺CH₃ methyl group, and the rest is due to the additive shift effects of the various C‐alkyl substituents of the piperidine ring. The shift effects of the C‐alkyl substituents in the amines, the N‐oxides and the methiodides are discussed. Copyright © 2007 John Wiley & Sons, Ltd.

The ¹³C NMR chemical shifts of (4aα,8aα, 9aβ, 10aα)‐, (4aα,8aα,9aα, 10aβ)‐ and (4aα,8aβ,9aα, 10aβ)‐tetradecahydroacridine were measured and fully assigned on the basis of APT, ¹³C, ¹H shift correlation and 2D‐INADEQUATE spectra.

Hydroacridines, XIII. — Steric Course of the N‐Oxidation of N‐Alkyl Derivatives of ((4aα,8aβ,9aβ,10aα)‐Tetradecahydroacridine (α‐Perhydroacridine)Diese Arbeit wurde auf der 5. rumänischen Konferenz für allgemeine und angewandte physikalische Chemie, Bukarest, 1. −4. September 1976, mitgeteilt. The oxidation of N‐methyl‐α‐perhydroacridine (1), with hydrogen peroxide at room temperature occurs approximately with 83% by equatorial, and approximately with 17% by axial attack of the oxygen on the nitrogen atom. The oxidations of N‐ethyl‐ (2) and N‐benzyl‐α‐perhydroacridine (3) yield only the N‐oxides with axial oxygen (2′a and 3′a, respectively).